The remains of the plane have been taken out of the building and away from the crash site. The National Transportation Safety Board will take all the pieces and place them in a warehouse where they will lay everything out and examine each one of them.
The man behind the controls of that single-engine plane was 45-year-old David Houghton. His wife and two boys were on board and they were headed to Pine Lake Mountain, 26 miles west of Yosemite, to meet up with the rest of their family.
Investigators from the National Transportation Safety Board and the Federal Aviation Administration combed through the debris and interviewed witnesses.
The plane took off Thursday night from the Watsonville Municipal Airport. Shortly after that, the plane went down crashing into the parking lot of the medical building, hitting the building. Fortunately, there was no one was inside the building at the time. Investigators will not speculate what could have happened. It's too early to say, but they will have a preliminary report in about five to 10 days.
"I can tell you the airplane appears to be all there with the exception of one propeller blade. What we look for in an aircraft is, we call it the four corners of the airplane, the nose, the two wing tips and the tail," said Michael Hugh, a NTSB air safety investigator.
Pilot Darrell Lewis, who has flown out of that airport, said, "It appears as though they went into a steep climb, perhaps stalling the airplane, and installing that airplane making a slow turn it's typical that the airplane will lost lift. And that's what it looks like."
That's up to investigators to determine, whether it was human or mechanical error or if the weather had anything to do with it.
Currently, there are four people conducting this investigation, but they might call in other people such as the makers of the plane or the engine manufacturer or weather experts. So this investigation will take time.
This is a very hard time for everyone who knows the Houghton family. They've been a fixture in Santa Cruz for decades. In fact, David's father was a professor at U.C. Santa Cruz and David graduated from that school.
David started flying a few years ago and bought his plane last year. Since then, the family has travelled all over in that four passenger plane. David's brother thinks he left at 7:30 to likely beat the fog and darkness and moments after takeoff, the engine may have started sputtering and failed.
"It just seems like we're going to see him walk in the door, or you're going to see him showing up. It's funny how time works and how someone can be there one minute and not be there the next," said John Houghton, David's brother.
"I know he would be gratified to know that nobody else got hurt. Knowing Dave, I know that that's important to him," said David Ghilarducci, a family friend.
Investigators say the family of four died instantly. And no one else on the ground was hurt. David, Dee Dee, and their sons all loved the air and the water. They were constantly scuba diving and flying. The couple owned a scuba school and an environmental services company in Santa Cruz.
The Houghtons were also very altruistic. They recently raised money and sent supplies to a small community in Mexico which was devastated by a hurricane.
Earlier on Friday, witnesses told ABC7 they could tell the plane was in trouble because it was wobbling. It hit in a parking lot, skidded into a medical office building on the campus of the Watsonville Community Hospital, and the plane exploded on impact.
"The airplane hit and there was a big explosion. The explosion was taller than the antennas you guys got," said witness Ivan Guerrero.
Guerrero watched helplessly as the plane crashed into the medical offices.
"They were in there burning. There was nothing I could do. All I could do was watch. Everybody was calling (for help). When the ambulance showed up they had been burning for awhile. That's really sad," said Guerrero.
As investigators visited the site of the crash, so did a steady stream of Watsonville residents. Hospital employee Pam Peck was in the office next door just before the crash. She gets emotional just thinking about it.
"I left shortly before, which is always a flash in one's life. I'm lucky, I think my greatest emotion is that I'm very glad that it happened at the time of day that it was and that it did not hit the hospital," said Peck.
The Watsonville Community Hospital was spared -- the plane missed the hospital's main building. The staff is conducting business as usual today.
"We have a great team here at this hospital and there really is a sense of calm - probably a little bit of thankfulness that it didn't hit any part of the hospital proper," said hospital spokeswoman Cindy Weigelt.